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Yang K, Zhao G, Li H, Tian X, Xu L, Yan J, Xie X, Yan Y, Yang M. Modification of Yarrowia lipolytica via metabolic engineering for effective remediation of heavy metals from wastewater. JOURNAL OF HAZARDOUS MATERIALS 2024; 476:134954. [PMID: 38936184 DOI: 10.1016/j.jhazmat.2024.134954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 06/11/2024] [Accepted: 06/16/2024] [Indexed: 06/29/2024]
Abstract
With the increasing demand for heavy metals due to the advancement of industrial activities, large proportions of heavy metals have been discharged into aquatic ecosystems, causing serious harm to human health and the environment. Existing physical and chemical methods for recovering heavy metals from wastewater encounter challenges, such as low efficiency, high processing costs, and potential secondary pollution. In this study, we developed a novel approach by engineering the endogenous sulphur metabolic pathway of Yarrowia lipolytica, providing it with the ability to produce approximately 550 ppm of sulphide. Subsequently, sulphide-producing Y. lipolytica was used for the first time in heavy metal remediation. The engineered strain exhibited a high capacity to remove various heavy metals, especially achieving over 90 % for cadmium (Cd), copper (Cu) and lead (Pb). This capacity was consistent when applied to both synthetic and actual wastewater samples. Microscopic analyses revealed that sulphide-mediated biological precipitation of metal sulphides on the cell surface is responsible for their removal. Our findings demonstrate that sulphide-producing yeasts are a robust and effective bioremediation strategy for heavy metals, showing great potential for future heavy metal pollution remediation practices.
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Affiliation(s)
- Kaixin Yang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Guowei Zhao
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Huanhuan Li
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xiaoke Tian
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Li Xu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Jinyong Yan
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xiaoman Xie
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Yunjun Yan
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
| | - Min Yang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
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Yang Y, Liu LN, Tian H, Cooper AI, Sprick RS. Making the connections: physical and electric interactions in biohybrid photosynthetic systems. ENERGY & ENVIRONMENTAL SCIENCE 2023; 16:4305-4319. [PMID: 38013927 PMCID: PMC10566253 DOI: 10.1039/d3ee01265d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 08/14/2023] [Indexed: 11/29/2023]
Abstract
Biohybrid photosynthesis systems, which combine biological and non-biological materials, have attracted recent interest in solar-to-chemical energy conversion. However, the solar efficiencies of such systems remain low, despite advances in both artificial photosynthesis and synthetic biology. Here we discuss the potential of conjugated organic materials as photosensitisers for biological hybrid systems compared to traditional inorganic semiconductors. Organic materials offer the ability to tune both photophysical properties and the specific physicochemical interactions between the photosensitiser and biological cells, thus improving stability and charge transfer. We highlight the state-of-the-art and opportunities for new approaches in designing new biohybrid systems. This perspective also summarises the current understanding of the underlying electron transport process and highlights the research areas that need to be pursued to underpin the development of hybrid photosynthesis systems.
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Affiliation(s)
- Ying Yang
- Materials Innovation Factory and Department of Chemistry, University of Liverpool Liverpool L7 3NY UK
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool Liverpool L69 7ZB UK
| | - Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool Liverpool L69 7ZB UK
- College of Marine Life Sciences, and Frontiers Science Centre for Deep Ocean Multispheres and Earth System, Ocean University of China 266003 Qingdao P. R. China
| | - Haining Tian
- Department of Chemistry-Ångström Laboratories, Uppsala University Box 523 751 20 Uppsala Sweden
| | - Andrew I Cooper
- Materials Innovation Factory and Department of Chemistry, University of Liverpool Liverpool L7 3NY UK
| | - Reiner Sebastian Sprick
- Department of Pure and Applied Chemistry, University of Strathclyde Thomas Graham Building, 295 Cathedral Street Glasgow G1 1XL UK
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Tu JW, Li T, Gao ZH, Xiong J, Miao W. Construction of CdS-Tetrahymena thermophila hybrid system by efficient cadmium adsorption for dye removal under light irradiation. JOURNAL OF HAZARDOUS MATERIALS 2022; 439:129683. [PMID: 36104909 DOI: 10.1016/j.jhazmat.2022.129683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 07/12/2022] [Accepted: 07/25/2022] [Indexed: 06/15/2023]
Abstract
The water pollution caused by heavy metals and dyes emitted by industries has become a worldwide problem. These pollutants are difficult to be biodegraded. Even at low concentrations, they are toxic and at last threaten human health. Herein, while using Tetrahymena thermophila, a single-celled ciliate protozoa, to enrich and remove the heavy metal Cd2+ from water, CdS nanoparticle-Tetrahymena thermophila hybrid system (CdS-T. thermophila) for dye pollution remediation under light irradiation was developed. The conditions of Cd2+ enrichment and removal by T. thermophila, construction of efficient CdS-T. thermophila, and decolorization of Congo red using CdS-T. thermophila were investigated. In the presence of cysteine ethyl ester, the removal rate of Cd2+ by T. thermophila was 94% at low Cd2+ concentration of 1 mg L-1. The adsorption capacity of T. thermophila to Cd2+ reached 43 mg g-1 at Cd2+ concentration of 80 mg L-1. Using 0.1 g L-1 constructed CdS-T. thermophila, the decolorization rate of 50 mg L-1 Congo red solution reached 95% in 60 min under light irradiation. This study provides a new insight to effective removing Cd2+ from water by T. thermophila to construct the CdS-T. thermophila and using it to remediate dye pollution in the environment.
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Affiliation(s)
- Jia-Wei Tu
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Tian Li
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zi-Han Gao
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jie Xiong
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Wei Miao
- Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
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Honda Y, Shinohara Y, Watanabe M, Ishihara T, Fujii H. Photo-biohydrogen Production by Photosensitization with Biologically Precipitated Cadmium Sulfide in Hydrogen-Forming Recombinant Escherichia coli. Chembiochem 2020; 21:3389-3397. [PMID: 32697401 DOI: 10.1002/cbic.202000383] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 07/17/2020] [Indexed: 11/10/2022]
Abstract
An inorganic-biological hybrid system that integrates features of both stable and efficient semiconductors and selective and efficient enzymes is attractive for facilitating the conversion of solar energy to hydrogen. In this study, we aimed to develop a new photocatalytic hydrogen-production system based on Escherichia coli whole-cell genetically engineered as a biocatalysis for highly active hydrogen formation. The photocatalysis part was obtained by bacterial precipitation of cadmium sulfide (CdS), which is a visible-light-responsive semiconductor. The recombinant E. coli cells were sequentially subjected to CdS precipitation and heterologous [FeFe]-hydrogenase synthesis to yield a CdS@E. coli hybrid capable of light energy conversion and hydrogen formation in a single cell. The CdS@E. coli hybrid achieved photocatalytic hydrogen production with a sacrificial electron donor, thus demonstrating the feasibility of our system and expanding the current knowledge of photosensitization using a whole-cell biocatalyst with a bacterially precipitated semiconductor.
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Affiliation(s)
- Yuki Honda
- Department of Chemistry, Biology, and Environmental Science, Faculty of Science, Nara Women's University, Kitauoyanishi-machi, Nara, 630-8506, Japan
| | - Yuka Shinohara
- Department of Chemistry, Biology, and Environmental Science, Faculty of Science, Nara Women's University, Kitauoyanishi-machi, Nara, 630-8506, Japan
| | - Motonori Watanabe
- International Institute for Carbon-Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Tatsumi Ishihara
- International Institute for Carbon-Neutral Energy Research, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan.,Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, 819-0395, Japan
| | - Hiroshi Fujii
- Department of Chemistry, Biology, and Environmental Science, Faculty of Science, Nara Women's University, Kitauoyanishi-machi, Nara, 630-8506, Japan
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Marusak KE, Krug JR, Feng Y, Cao Y, You L, Zauscher S. Bacterially driven cadmium sulfide precipitation on porous membranes: Toward platforms for photocatalytic applications. Biointerphases 2018; 13:011006. [PMID: 29426227 PMCID: PMC5807096 DOI: 10.1116/1.5008393] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2017] [Revised: 01/11/2018] [Accepted: 01/19/2018] [Indexed: 11/17/2022] Open
Abstract
The emerging field of biofabrication capitalizes on nature's ability to create materials with a wide range of well-defined physical and electronic properties. Particularly, there is a current push to utilize programmed, self-organization of living cells for material fabrication. However, much research is still necessary at the interface of synthetic biology and materials engineering to make biofabrication a viable technique to develop functional devices. Here, the authors exploit the ability of Escherichia coli to contribute to material fabrication by designing and optimizing growth platforms to direct inorganic nanoparticle (NP) synthesis, specifically cadmium sulfide (CdS) NPs, onto porous polycarbonate membranes. Additionally, current, nonbiological, chemical synthesis methods for CdS NPs are typically energy intensive and use high concentrations of hazardous cadmium precursors. Using biosynthesis methods through microorganisms could potentially alleviate these issues by precipitating NPs with less energy and lower concentrations of toxic precursors. The authors adopted extracellular precipitation strategies to form CdS NPs on the membranes as bacterial/membrane composites and characterized them by spectroscopic and imaging methods, including energy dispersive spectroscopy, and scanning and transmission electron microscopy. This method allowed us to control the localization of NP precipitation throughout the layered bacterial/membrane composite, by varying the timing of the cadmium precursor addition. Additionally, the authors demonstrated the photodegradation of methyl orange using the CdS functionalized porous membranes, thus confirming the photocatalytic properties of these composites for eventual translation to device development. If combined with the genetically programmed self-organization of cells, this approach promises to directly pattern CdS nanostructures on solid supports.
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Affiliation(s)
- Katherine E Marusak
- Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall Box 90300, Durham, North Carolina 27708
| | - Julia R Krug
- Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall Box 90300, Durham, North Carolina 27708
| | - Yaying Feng
- Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall Box 90300, Durham, North Carolina 27708
| | - Yangxiaolu Cao
- Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham, North Carolina 27708
| | - Lingchong You
- Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham, North Carolina 27708; Center for Genomic and Computational Biology, Duke University, 101 Science Drive, Durham, North Carolina 27708; and Department of Molecular Genetics and Microbiology, Duke University School of Medicine, DUMC 3710, Durham, North Carolina 27710
| | - Stefan Zauscher
- Department of Mechanical Engineering and Materials Science, Duke University, 144 Hudson Hall Box 90300, Durham, North Carolina 27708 and Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham, North Carolina 27708
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Marusak KE, Feng Y, Eben CF, Payne ST, Cao Y, You L, Zauscher S. Cadmium sulphide quantum dots with tunable electronic properties by bacterial precipitation. RSC Adv 2016; 6:76158-76166. [PMID: 28435671 DOI: 10.1039/c6ra13835g] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We present a new method to fabricate semiconducting, transition metal nanoparticles (NPs) with tunable bandgap energies using engineered Escherichia coli. These bacteria overexpress the Treponema denticola cysteine desulfhydrase gene to facilitate precipitation of cadmium sulphide (CdS) NPs. Analysis with transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy reveal that the bacterially precipitated NPs are agglomerates of mostly quantum dots, with diameters that can range from 3 to 15 nm, embedded in a carbon-rich matrix. Additionally, conditions for bacterial CdS precipitation can be tuned to produce NPs with bandgap energies that range from quantum-confined to bulk CdS. Furthermore, inducing precipitation at different stages of bacterial growth allows for control over whether the precipitation occurs intra- or extracellularly. This control can be critically important in utilizing bacterial precipitation for the environmentally-friendly fabrication of functional, electronic and catalytic materials. Notably, the measured photoelectrochemical current generated by these NPs is comparable to values reported in the literature and higher than that of synthesized chemical bath deposited CdS NPs. This suggests that bacterially precipitated CdS NPs have potential for applications ranging from photovoltaics to photocatalysis in hydrogen evolution.
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Affiliation(s)
- K E Marusak
- Department of Mechanical Engineering & Materials Science, 144 Hudson Hall, Box 90300 Durham, NC 27708, United States
| | - Y Feng
- Department of Mechanical Engineering & Materials Science, 144 Hudson Hall, Box 90300 Durham, NC 27708, United States
| | - C F Eben
- Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham NC 27708, United States
| | - S T Payne
- Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham NC 27708, United States
| | - Y Cao
- Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham NC 27708, United States
| | - L You
- Department of Biomedical Engineering, Duke University, 101 Science Drive, Durham NC 27708, United States
| | - S Zauscher
- Department of Mechanical Engineering & Materials Science, 144 Hudson Hall, Box 90300 Durham, NC 27708, United States
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7
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El-Baz AF, Sorour NM, Shetaia YM. Trichosporon jirovecii-mediated synthesis of cadmium sulfide nanoparticles. J Basic Microbiol 2015; 56:520-30. [PMID: 26467054 DOI: 10.1002/jobm.201500275] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 09/26/2015] [Indexed: 11/09/2022]
Abstract
Cadmium sulphide is one of the most promising materials for solar cells and of great interest due to its useful applications in photonics and electronics, thus the development of bio-mediated synthesis of cadmium sulphide nanoparticles (CdS NPs) is one of the essential areas in nanoparticles. The present study demonstrates for the first time the eco-friendly biosynthesis of CdS NPs using the yeast Trichosporon jirovecii. The biosynthesis of CdS NPs were confirmed by UV-Vis spectrum and characterized by X-ray diffraction assay and electron microscopy. Scanning and transmission electron microscope analyses shows the formation of spherical CdS NPs with a size range of about 6-15 nm with a mean Cd:S molar ratio of 1.0:0.98. T. jirovecii produced hydrogen sulfide on cysteine containing medium confirmed by positive cysteine-desulfhydrase activity and the colony color turned yellow on 0.1 mM cadmium containing medium. T. jirovecii tolerance to cadmium was increased by the UV treatment and three 0.6 mM cadmium tolerant mutants were generated upon the UV radiation treatment. The overall results indicated that T. jirovecii could tolerate cadmium toxicity by its conversion into CdS NPs on cysteine containing medium using cysteine-desulfhydrase as a defense response mechanism.
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Affiliation(s)
- Ashraf Farag El-Baz
- Department of Industrial Biotechnology, Genetic Engineering and Biotechnology Research Institute, University of Sadat City, Sadat City, Egypt
| | - Noha Mohamed Sorour
- Department of Industrial Biotechnology, Genetic Engineering and Biotechnology Research Institute, University of Sadat City, Sadat City, Egypt
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Villa-Gomez D, Ababneh H, Papirio S, Rousseau DPL, Lens PNL. Effect of sulfide concentration on the location of the metal precipitates in inversed fluidized bed reactors. JOURNAL OF HAZARDOUS MATERIALS 2011; 192:200-207. [PMID: 21664045 DOI: 10.1016/j.jhazmat.2011.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Revised: 04/04/2011] [Accepted: 05/02/2011] [Indexed: 05/30/2023]
Abstract
The effect of the sulfide concentration on the location of the metal precipitates within sulfate-reducing inversed fluidized bed (IFB) reactors was evaluated. Two mesophilic IFB reactors were operated for over 100 days at the same operational conditions, but with different chemical oxygen demand (COD) to SO(4)(2-) ratio (5 and 1, respectively). After a start up phase, 10mg/L of Cu, Pb, Cd and Zn each were added to the influent. The sulfide concentration in one IFB reactor reached 648 mg/L, while it reached only 59 mg/L in the other one. In the high sulfide IFB reactor, the precipitated metals were mainly located in the bulk liquid (as fines), whereas in the low sulfide IFB reactor the metal preciptiates were mainly present in the biofilm. The latter can be explained by local supersaturation due to sulfide production in the biofilm. This paper demonstrates that the sulfide concentration needs to be controlled in sulfate reducing IFB reactors to steer the location of the metal precipitates for recovery.
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Affiliation(s)
- D Villa-Gomez
- Core Pollution Prevention and Control, UNESCO-IHE, Institute for Water Education, PO Box 3015, 2601 DA Delft, The Netherlands.
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Bai H, Zhang Z, Guo Y, Jia W. Biological Synthesis of Size-Controlled Cadmium Sulfide Nanoparticles Using Immobilized Rhodobacter sphaeroides. NANOSCALE RESEARCH LETTERS 2009; 4:717-723. [PMID: 20596372 PMCID: PMC2894101 DOI: 10.1007/s11671-009-9303-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Accepted: 03/24/2009] [Indexed: 05/28/2023]
Abstract
Size-controlled cadmium sulfide nanoparticles were successfully synthesized by immobilized Rhodobacter sphaeroides in the study. The dynamic process that Cd(2+) was transported from solution into cell by living R. sphaeroides was characterized by transmission electron microscopy (TEM). Culture time, as an important physiological parameter for R. sphaeroides growth, could significantly control the size of cadmium sulfide nanoparticles. TEM demonstrated that the average sizes of spherical cadmium sulfide nanoparticles were 2.3 +/- 0.15, 6.8 +/- 0.22, and 36.8 +/- 0.25 nm at culture times of 36, 42, and 48 h, respectively. Also, the UV-vis and photoluminescence spectral analysis of cadmium sulfide nanoparticles were performed.
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Affiliation(s)
- Hongjuan Bai
- Chemical Industry and Ecology Institute, North University of China, Taiyuan, 030051, China
| | - Zhaoming Zhang
- College of Life Science and Technology, Shanxi University, Taiyuan, 030006, China
| | - Yu Guo
- Chemical Industry and Ecology Institute, North University of China, Taiyuan, 030051, China
| | - Wanli Jia
- Chemical Industry and Ecology Institute, North University of China, Taiyuan, 030051, China
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van Hullebusch ED, Gieteling J, Van Daele W, Defrancq J, Lens PN. Effect of sulfate and iron on physico-chemical characteristics of anaerobic granular sludge. Biochem Eng J 2007. [DOI: 10.1016/j.bej.2006.10.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Silver S, Phung LT. A bacterial view of the periodic table: genes and proteins for toxic inorganic ions. J Ind Microbiol Biotechnol 2005; 32:587-605. [PMID: 16133099 DOI: 10.1007/s10295-005-0019-6] [Citation(s) in RCA: 253] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Accepted: 07/11/2005] [Indexed: 10/25/2022]
Abstract
Essentially all bacteria have genes for toxic metal ion resistances and these include those for Ag+, AsO2-, AsO4(3-), Cd2+ Co2+, CrO4(2-), Cu2+, Hg2+, Ni2+, Pb2+, TeO3(2-), Tl+ and Zn2+. The largest group of resistance systems functions by energy-dependent efflux of toxic ions. Fewer involve enzymatic transformations (oxidation, reduction, methylation, and demethylation) or metal-binding proteins (for example, metallothionein SmtA, chaperone CopZ and periplasmic silver binding protein SilE). Some of the efflux resistance systems are ATPases and others are chemiosmotic ion/proton exchangers. For example, Cd2+-efflux pumps of bacteria are either inner membrane P-type ATPases or three polypeptide RND chemiosmotic complexes consisting of an inner membrane pump, a periplasmic-bridging protein and an outer membrane channel. In addition to the best studied three-polypeptide chemiosmotic system, Czc (Cd2+, Zn2+, and Co2), others are known that efflux Ag+, Cu+, Ni2+, and Zn2+. Resistance to inorganic mercury, Hg2+ (and to organomercurials, such as CH3Hg+ and phenylmercury) involve a series of metal-binding and membrane transport proteins as well as the enzymes mercuric reductase and organomercurial lyase, which overall convert more toxic to less toxic forms. Arsenic resistance and metabolizing systems occur in three patterns, the widely-found ars operon that is present in most bacterial genomes and many plasmids, the more recently recognized arr genes for the periplasmic arsenate reductase that functions in anaerobic respiration as a terminal electron acceptor, and the aso genes for the periplasmic arsenite oxidase that functions as an initial electron donor in aerobic resistance to arsenite.
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Affiliation(s)
- Simon Silver
- Department of Microbiology and Immunology, University of Illinois, Chicago, IL 60612, USA.
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Abstract
Inverse metabolic engineering (IME) is a powerful framework for engineering cellular phenotypes. Progress in this field has been limited by a lack of comprehensive methods for efficiently identifying the genetic basis of relevant phenotypes. Advances in genomics technologies, including DNA microarrays and gene sequencing, have dramatically improved our ability to relate changes in phenotype with associated changes in genotype. When applied in the context of IME, these tools should enable the integration of "evolutionary" and "direct" approaches to engineering cell physiology, which should improve our understanding of the complex interactions affecting the expression, evolution and engineering of traits in natural and industrial hosts.
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Affiliation(s)
- Ryan T Gill
- Department of Chemical and Biological Engineering, UCB 424/ECCH120, University of Colorado, Boulder, CO 80304, USA.
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